This invention relates to a fluid delivery system for delivering a plurality of fluids, in sequence to one or more treatment reservoirs.
Prior to the present invention, fluid delivery systems have been available which minimize intermixing of fluids while delivering a precise amount of a fluid for chemical reaction. These systems are generally utilized for chemical processes involving a large number of sequentially effected chemical reactions such as in protein synthesis, DNA synthesis or when sequencing proteins.
U.S. Pat. No. 4,008,736 discloses a valve block containing a capillary formed of capillary segments bored at about 30.degree. from a contact surface of the block. The junctions of the capillary segments are effected at the contact surface and within the block. The junctions at the contact surfaces form valving sites to which are engaged apertured sliding blocks which effect fluid communication with the capillary. While the sliding blocks are effective in providing the desired fluid flow, they wear too rapidly thereby causing undesirable leaks.
U.S. Pat. No. 4,168,724 discloses a similar device but replaces the slider valves with diaphragm valves. The fluid is delivered through the valves from a pressurized fluid storage source. This system requires a vacuum assist to open the valves. This system is undesirable because the type of diaphragm valve used is undesirably susceptible to particulate contamination. In addition, the pressure drop through the valves is difficult to control which causes less accurate reagent delivery.
U.S. Pat. No. 4,558,845 discloses a fluid delivery system utilizing a valve block assembly comprising a separate block for each valve site. The common conduit to the reaction site is alternately a channel in a block and tubing connecting two adjacent blocks. This arrangement requires a plurality of fittings which are subject to leaking.
U.S. Pat. No. 4,773,446 discloses a valve block assembly which utilizes diaphragm valves. The valves serve to control fluid flow from a plurality of pressurized fluid reservoirs, in sequence to a common outlet reservoir. This system requires the use of conduits from the fluid reservoirs and fittings to valve blocks for each conduit.
The fluid delivery system of the prior art depend upon the use of positive pressure to deliver the fluid and upon the control of back pressure to the fluid reservoir in order to precisely control the amount of fluid delivered to a treatment reservoir. These systems require the frequent adjustment of the fluid delivery means as a function of back pressure. All of the systems set forth above depend upon the precise control of reservoir pressure and restriction through the tubing, channels, and valves to control reagent delivery volume. They are very sensitive to variations of the removable reaction columns as regards the delivery volume and flow rate. Also, these systems deliver fluids against backpressures only up to about 10 psig.
U.S. Pat. No. 5,123,443 discloses a system for delivering a plurality of fluids in sequence to a treatment reservoir, comprising a plurality of pumps in fluid communication with other via passages in a solid plate. Each pump is comprised of a diaphragm member that effects transport by forcing fluid out of a plenum cavity; an injector (check valve) that opens in response to a threshold pressure to allow escape of fluid into a common passage; and an inlet check valve that closes in response to rising pressure but otherwise allows the plenum cavity of the diaphragm member to refill. The performance of these passive check valves in pumps of very small volume is marginal because even very small leaks greatly dampen the pressure transients to which these check valves respond. The worst case situation is the attempt to pump a low viscosity, compressible fluid (i.e., gas), wherein the pumps may display difficulty in priming due to microscopic leaks.
Copending U.S. patent application Ser. No. 07/655,012, filed Feb. 14, 1991, and entitled "Conduit Plate for Fluid Delivery System" discloses a conduit plate for a fluid delivery system comprising four or five layers laminated together, including a plurality of notched openings for attaching external fluid processing components in fluid communication with the plate; and a single fluid conduit layer for effecting passage of fluids between different points on the solid plate. The plate, preferentially is formed of a ceramic material. A plurality of fluids are delivered in sequence to a desired point by means of a plurality of pumps, each comprising a diaphragm member, an injector (a passive outlet check valve), and an inlet check valve. The notched openings in the plate address a problem inherent in the manufacture of the solid plate wherein the dimensional tolerances of the solid plate are comparable or larger than the dimensions of the passages within the plate so that mating parts can be aligned accurately only insofar as the plate itself serves to key the positions of external components mating to said plate. However, direct attachment of components to the solid plate places the solid plate under tensional forces that may cause breakage. The presence of a single conduit layer in the solid plate results in unique layout of fluid passages in the plate because passages cannot cross each other, and revisions in the fluid path are correspondingly made more difficult. Apparatus which utilize these plates are disclosed in U.S. Pat. Nos. 5,095,932; 5,095,938; 5,111,845 and 5,123,443.
It would be desirable to provide a system which eliminates the need of adjustment of the fluid delivery means. It would also be desirable to utilize a means to deliver accurate fluid volumes which is insensitive to back pressure. Such a system would result in improved system performance and reduced reagent consumption. It would also be desirable to provide a fluid delivery system which minimizes the use of tubes and tube fittings while minimizing the volume of the system as compared to presently available systems. In addition, it would be desirable to provide a fluid delivery system which can be easily primed so that even gases can be pumped easily.